Diffrenec between Have not and had not?

"Have not" is the present perfect tense, indicating a lack of possession or experience up to the present moment, such as in "I have not finished my homework." In contrast, "had not" is the past perfect tense, used to describe a lack of possession or experience before a certain point in the past, like in "I had not finished my homework before the deadline." Essentially, "have not" relates to the present, while "had not" relates to the past.